1. Field of the Invention
The present invention relates in general to data storage systems such as disk drives, and it particularly relates to a thin film read/write head for use in such data storage systems. More specifically, the present invention relates to a thin film, inductive type write head with a stitched yoke, a curved apex region, and a top yoke geometry defined on a planar surface.
2. Description of Related Art
In a conventional magnetic storage system, a thin film magnetic head includes an inductive read/write element mounted on a slider. The magnetic head is coupled to a rotary actuator magnet and a voice coil assembly by a suspension and an actuator arm positioned over a surface of a spinning magnetic disk. In operation, a lift force is generated by the aerodynamic interaction between the magnetic head and the spinning magnetic disk. The lift force is opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disk.
An exemplary magnetic head includes a thin film write head with a bottom pole (P1) and a top pole (P2). The poles P1 and P2 have a pole tip height dimension commonly referred to as xe2x80x9cthroat heightxe2x80x9d. In a finished write head, the throat height is measured between an air bearing surface (xe2x80x9cABSxe2x80x9d), formed by lapping and polishing the pole tip, and a zero throat level where the pole tip of the write head transitions to a back region. A pole tip region is defined as the region between the ABS and the zero throat level. Each of the poles P1 and P2 has a pole tip located in the pole tip region. The tip regions of the poles P1 and P2 are separated by a magnetic recording gap, which is a thin layer of insulation material.
A significant concern with the design of the magnetic head is to accurately control the dimensions of the top pole P2 in order to maximize the aerial density of the recording medium. This task has been particularly difficult to accomplish in view of the irregular topography of the inductive coil layer underlying the top pole P2. Such irregular topography is introduced during fabrication of the insulation layers that sandwich the coil structure and that flow into the pole tip region. As a result, when high moment material is sputter deposited on such uneven areas, soft spots develop and adversely affect the magnetic performance of the head.
In addition, it has been difficult to define the pole P2 with a tip less than 2 microns in width. This is because the width of the top pole P2 at the pole tip region is typically defined after placement of the coil structure, one or more insulation layers and the top pole layer. The width of the tip of pole P2 is defined by forming a thick photoresist mask on top of the pole P2 and then etching the width configuration at the pole tip region. The thickness of the resist layer has to be 20 microns or more in order to protect the pole P2 from ion bombardment. The thickness of the resist needs to be sufficient to either protect the pole piece during etching steps, or thick enough to xe2x80x9ccontainxe2x80x9d the plated feature when pattern plating is used. Also, because of the topography of the device the resist tends to get much thicker than desirable in the region near the zero throat of the head, due to the dynamics of the resist coating process. The thicker the resist the more difficult it is to accurately control the dimensions of the resist, and it becomes very difficult to produce poles of less than 2 microns.
Another design concern with thin film write heads is the precise positioning of the zero throat level. Because of the difficulty in maintaining well defined frontal configurations of the top insulation layer and the top pole layer at the zero throat level, the zero throat level does not lie is a well defined plane which is parallel to the plane of the ABS. This problem is further exasperated by the dimensional changes that are effectuated by the curing process of the photoresist layers.
Still another design concern relates to the flux leakage between the two poles P1 and P2 at the back portion of the pole tip region, at, or in close proximity to the zero throat level. This is because the slope of the insulating layer in that area is gradual and the poles P1 and P2 are gradually or not sufficiently separated.
Attempts have been made to alleviate.the foregoing concerns. One such attempt is exemplified by U.S. Pat. No. 5,649,351 to Cole et al., which is incorporated herein by reference. The Cole et al. patent describes a thin film magnetic write head and method wherein the write head has a pole tip region between the planar ABS and the zero throat level. The write head has a yoke that includes top and bottom magnetic poles. Each pole has a pole tip structure in the pole tip region. The pole tip structure of the bottom pole has bottom and top pole tip elements PT1a and PT1b and the pole tip structure of the top pole has a top and bottom pole tip elements PT2a and PT2b. The pole tip elements PT1b and PT2b are located between the pole tip elements PT1a and PT2a and a gap layer G is located between the pole tip elements PT1b and PT2b. Each of the pole tip elements PT1b and PT2b and the gap layer G are bounded by front and back walls and first and second sidewalls. The first sidewalls of the pole tip elements PT1b and PT2b and the gap layer G are aligned with respect to one another and the second sidewalls of the pole tip elements PT1b and PT2b and the gap layer G are aligned with respect to one another. The front walls of the pole tip elements PT1b and PT2b and the gap layer G lie in a common plane which forms a portion of the ABS. The back walls of the pole tip elements PT1b and PT2b and the gap layer G lie in a common plane which forms the zero throat level. The common plane of the zero throat level is substantially parallel to the common plane of the ABS.
While the Wade et al. design may have addressed and resolved some of the foregoing design concerns, it is not completely satisfactory. Among other shortcomings, the back edge of the pole tip element PT2b in the Wade et al. head defines the back edge of the gap G, such that the dimensions, i.e., the length and width of the pole tip element PT2b, have to be defined and formed simultaneously in a single step.
Furthermore, the pole tip element PT2a in the Wade et al. head is stitched to the pole tip element PT2b at the ABS level. If the stitch at the ABS were not adequate, it can create a secondary gap capable of writing and inducing noise onto the medium. Furthermore, the presence of a weakness in the stitch at the ABS might eventually lead to a physical separation of the two pole tip elements PT2a and PT2b, resulting in a fringe field that generates undesirable noise.
One aspect of the present invention is to satisfy the long felt, and still unsatisfied need for thin film read/write head with a high performance inductive write section that demonstrates good physical pole tip geometry control and is simple and economical to process.
The head delineates an air bearing surface, and includes a pedestal formed on a read section. The pedestal includes a back edge that defines a zero throat level which lies in a plane substantially parallel to the air bearing surface. A pole layer is formed over, and separated from the pedestal to define a write gap therebetween. The pole layer includes an angled edge so that a top yoke can be stitched therealong to the pole layer.